Polls are open in Arizona and, as 12 News and the Arizona Republic note, one of the hardest-fought battles in the state is between GOP incumbent Attorney General Tom Horne and challenger Mark Brnovich.

Even in politics, the Arizona race has set a new standard for nasty: responding to accusations of personal and professional wrongdoing, Horne has attacked his opponent as soft on immigration. Horne has attempted to tie his opponent’s position on immigration to President Barack Obama’s, and said in one ad that, “Brnovich supported a leader in the open borders movement.”

Despite the noise on immigration emanating from the Horne campaign, voters haven’t been able to escape the reminder that their sitting AG has been at the center of serial scandals since taking office.

If Horne can survive the attacks on his behavior, it might suggest that the immigration is still radioactive.

That outcome tonight would be a strong signal that immigration is priority No. 1, especially for Republicans, which isn’t something that should be ignored by either party heading into the November midterms.